At the same time, and like many of the French educated young men of his generation, he enters a far-left party, the trotskyistUCI. That particular brand of trotskyism prepares the Revolution by infiltrating its members in potentially friendly left-leaning organisations; as such, Lionel Jospin enters the Socialist Party just as it is founded by Francois Mitterrand in 1971. However ever since he has tried to hide his belonging to the UCI; it is certain he is no more affiliated with that organisation, but nobody really knows when he decided to become a member of the PS for its own sake.

It should be noted that his career in the Party was going on very well; he had been given the important role of negociating a common platform with the Communist Party, an essential alliance if Mitterrand was to become President of the Repblic. When that happened, in 1981, Jospin became the first secretary of the PS; in effect, he was ruling the party while Mitterrand was ruling France. After Mitterrand's reelection in 1988, he became Minister of Education, and remained in that position until the Left's whooping defeat in the 1993 parliamentary elections. At that point Jospin thought of abandoning politics, and of reintegrating the Foreign Affairs corpse. The rightist Minister of the time, Alain Juppé, didn't let him in fast enough, and after Jacques Delors's refusal of running in the 1995 Presidential Elections, Jospin became the prime contender for the Socialist Party.

Even though he overall lost that election, he was still able to pass on the second round, polling the first place in the first round, a result much better than expected after the huge margin of defeat for the left in 1993. He was then the contender for Prime Minister for the left, after the next parliamentary elections which were to be held in 1998. The new President, Jacques Chirac, decided however, being probably overconfident in the polls, decided to hold these elections a year earlier; and in 1997 the Left won those elections and thus Lionel Jospin became Prime Minister.

The five next years he spent governing France were not a perfect success, yet he certainly performed better than average; he was able to reduce the workweek to 35 hours, to institute a kind of homosexual marriage, unemployment went down, the Economy grew... It was obvious to everyone the 2002 Presidential Elections would see Jospin and Chirac facing each other on the second round. However, the fact that Jospin's platform was a bit too centrist left a wide political space for many spoiler candidates on the left, and the vote for Jean-Marie Le Pen, the far-right candidate, was much higher than expected; on
April the 23nd of 2002, Jospin was eliminated from the Presidential Elections, and by 10 pm had announced his retirement from political life.

His political stance was of a moderate left; in the 2002 campaign, he expressly said his platform was "not Socialist", a move that cost him many votes. However that moderate left wasn't as moderate as that of Gerarhd Schröder or Tony Blair, he didn't believe in a Clintonian "Third Way" between Social-Democracy and Liberalism. His image was that of an honest, puritanical man, close to the French cliché of protestantism. He offered a striking contrast to his opponent Chirac, who is seen as deeply corrupt but also much more charismatic; the fact that he looked like a teacher, with his white curly hair and round glasses, didn't help him winning the popularity contest that elections are seemingly bound to become in our modern democracies.

Lionel Jospin retired from public life following his unexpected defeat in the first round of the French presidential election of 2002. With a score of only just over 16 per cent, Jospin was beaten into third place by traditional right-wing candidate and incumbant president Jacques Chirac who came first and by Jean-Marie le Pen, leader of the extreme right-wing Nationale Front.